Essentially I can get 60hz at 4k on my Mac Mini with a work around. On my Monitor I have a setting PIP/PBP This allows two input sources. Use HDMI and Display port into this giving you Side by Side Desktops. Making My Mac Mini think it has two Monitors connected to it at 1920 x 2160. I use App that then combines both Desktops to single Desktop. Only tested this on Windows at this moment. But want to see if I can get it working on OSX Obviosuly if I can get 60hz this way it is in theory possible with one cable but it has been limited.